Shift table for use in a product conveyor system having workstations

ABSTRACT

A workstation includes a support assembly with at least one longitudinally extending rail. A longitudinally extending conveyor is slidably mounted to the rail for sliding movement between a home position, where the conveyor is predominately provided for working on a workpiece, and a second position, where one end of the conveyor is provided adjacent to a conveyor line. The conveyor has a longitudinal length that allows an access space between the conveyor and one of the lines when the conveyor is provided in the home position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to workstations having conveyor systemsfor delivering workpieces to and from the workstations.

2. Description of the Related Art

In a computer production facility, an area A of the facility is oftendedicated to testing individual computer components. As illustrated inFIG. 1, the computer component testing area A often includes a supplyconveyor line B, a delivery conveyor line C and a plurality ofjuxtaposed workstations D that are positioned between the conveyor linesB, C. Each of the workstations D is supplied with computer componentsfor testing by the supply conveyor line B. After testing, the componentsare transferred to the delivery conveyor line C to be delivered forpackaging or further testing. In the past, to prevent the workers frombeing confined within the individual work areas E formed by the conveyorlines B and the adjacent workstations D, each of the workstations Dincluded a pivoting gravity gate F which operates in a manner similar toa drawbridge. The gravity gate F is lifted and pivoted by a worker to anopen or vertical position, as illustrated in FIG. 2, to allow accessinto or out of each of the work areas E. When the gravity gate F isopen, an access space G is provided between the workstation D and theconveyor line B through which the worker passes. After the worker passesthrough the access space G, the worker lowers the gravity gate F to aclosed or horizontal position. The workstation D may include a springarrangement to assist the workers in raising and lowering the gates F.

Although the gravity gates F allow access into and out of the work areasE, these gates F have multiple drawbacks. One drawback is that thegravity gates are potentially a safety hazard because they are noteasily or quickly opened in the event of a fire or other emergency.Another drawback is that the gravity gates F can fall and injure theworkers or damage the computer components. A further drawback is thateach gravity gate F includes exposed mechanisms that can cause injury toa worker manipulating the gravity gate F. Another problem is thatworkers often forget to close the gravity gates. As a result, computercomponents sometimes fall to the floor and become damaged. A furtherdrawback is that, even with a spring arrangement, raising and loweringthe gravity gates requires strenuous effort for some workers.

SUMMARY OF THE INVENTION

The workstation of the present invention includes a shifting conveyorthat eliminates the aforementioned problems with gravity gateworkstations. The shifting conveyor allows workers to freely pass intoand out of work areas without having to manipulate a gate. Allowing theworkers to freely pass into and out of work areas without a gate is moreconvenient, saves worker time, and eliminates the possibility of beingtrapped within a work area during a fire or other emergency. Without agate, the strenuous task of lifting and closing the gate, the potentialproblems caused by the gate accidentally falling on a worker orworkpiece, and the problems caused by a worker forgetting to close thegate are eliminated.

The above advantages are provided by a workstation that includes asupport assembly with at least one longitudinally extending rail. Alongitudinally extending conveyor is slidably mounted to the rail forsliding movement between a home position, where the conveyor ispredominantly provided for working on a workpiece, and a secondposition, where one end of the conveyor is provided adjacent to aconveyor line. The conveyor has a longitudinal length that allows anaccess space between the conveyor and one of the lines when the conveyoris in the home position.

One aspect of the present invention is a workstation for working on aworkpiece. The workstation comprises a support assembly which includesat least one longitudinally extending rail. A longitudinally extendingconveyor has opposite ends and is slidably mounted to the longitudinallyextending rail for slidable movement between at least a home positionwhere the conveyor is predominantly provided for working on theworkpiece and a second position where one end of the conveyor isprovided adjacent to a conveyor line. The conveyor has a longitudinallength that allows an access space between the conveyor and the conveyorline when the conveyor is provided in the home position. Preferably, theconveyor is slidably mounted to the rail by at least one slidablereceiver provided along an undersurface of the conveyor. The receiver isslidably mounted to the rail for sliding and shifting movement of theconveyor in a longitudinal and horizontal direction. Also preferably, apair of stop devices are provided near opposite ends of the conveyor toprevent the workpiece from accidentally falling off the conveyor. Eachof the stop devices includes a roller with a laterally and verticallyextending plate. In a preferred embodiment, the roller rotates in onlyone direction. A spring biases the stop plate to an upright position soas to prevent the workpiece from falling off the conveyor. Preferably,means for preventing a workpiece from falling off the conveyor isprovided near at least one end of the conveyor. The preventing means ismade ineffective when the conveyor is provided in at least the secondposition. Also preferably, the conveyor includes a locking mechanism.The locking mechanism cooperates with the supporting assembly to lockthe conveyor in the home and second positions.

Another aspect of the present invention is a worktable positionablebetween first and second conveyor lines. Products are conveyed betweenthe worktable and the first conveyor line and products are conveyedbetween the worktable and the second conveyor line. The worktablecomprises a top surface having a conveyor which permits products to bemoved across the top surface. A moveable support for the top surfacepermits lateral movement of the top surface from a first position wherethe top surface is proximate to the first conveyor line to a secondposition where the top surface is proximate to the second conveyor line.Preferably, sufficient space is provided between the worktable and thefirst conveyor line when the top surface is in the second position topermit a person to walk unimpeded between the worktable and the firstconveyor line.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described below in connection with theaccompanying drawing figures, in which:

FIG. 1 illustrates a top plan view of a computer component testing areaof the prior art and shows a number of the rotatable gravity gates ofthe workstations in an open position and the remainder of the gravitygates in a closed position;

FIG. 2 illustrates a perspective view of one of the prior artworkstations of FIG. 1 provided between a supply conveyor line anddelivery conveyor line and shows one gravity gate pivoted to an openposition and one in a closed position;

FIG. 3 illustrates a top plan view of a computer component testing area,similar to FIG. 1, and shows the workstations of the present inventionand the access space provided thereby between the workstations and oneof the conveyor lines;

FIG. 4 illustrates a perspective view of one of the workstations of FIG.3 provided between a supply conveyor line and delivery conveyor line andshows the conveyor of the workstation in a home position;

FIG. 5a illustrates a partial sectional view of one end of theworkstation and a portion of the delivery conveyor line taken alongsection 5 of FIG. 4 and shows the conveyor just prior to entering thehome position;

FIG. 5b illustrates a partial sectional view of one end of theworkstation and a portion of the delivery conveyor line, similar to FIG.5a, and shows an end roller in a slightly rotated position after beingcontacted by a projecting flange as the conveyor enters the homeposition;

FIG. 5c illustrates a partial sectional view of one end of theworkstation and a portion of the delivery conveyor line, similar to FIG.5a, and shows the end roller in a fully rotated position after beingcontacted by the projecting flange when the conveyor is fully in thehome position;

FIG. 6 illustrates a perspective view of the workstation providedbetween the supply conveyor line and the delivery conveyor line, similarto FIG. 4, and shows the conveyor shifted to a second or loadingposition adjacent to the supply conveyor line;

FIG. 7a illustrates a partial sectional view of one end of theworkstation and a portion of the supply conveyor line, taken alongsection 7 of FIG. 6, and shows the conveyor in a loading position, andshows a workpiece on the supply conveyor line;

FIG. 7b illustrates a partial sectional view of one end of theworkstation and a portion of the supply conveyor line, similar to FIG.7a, and shows an end roller in a partially rotated position after beingcontacted by the workpiece as it is loaded onto the conveyor;

FIG. 7c illustrates a partial sectional view of one end of theworkstation and part of one of the conveyor lines, similar to FIG. 7a,and shows the end roller in a fully rotated position after beingcontacted by the workpiece as it is loaded onto the conveyor;

FIG. 8 illustrates a top plan view of the conveyor with most of therollers removed so that the locking mechanism and other parts of theworkstation may be shown;

FIG. 9 illustrates an end view of the conveyor and a portion of theworkstation;

FIG. 10 illustrates an enlarged top view of the locking mechanism;

FIG. 11 illustrates a cross-sectional view of the locking mechanism,taken along line 11--11 of FIG. 10, and shows the locking mechanismengaged with a stop hole of a longitudinally extending beam;

FIG. 12 illustrates a cross-sectional view of the locking mechanism,similar to FIG. 11, and shows the locking mechanism disengaged from thestop hole of the longitudinally extending beam; and

FIG. 13 illustrates a cross-sectional view of the locking pin andU-shaped bracket of the locking mechanism taken along line 13--13 ofFIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 3 and 4 illustrate a computer component testing area, indicatedgenerally by the reference numeral 20. The testing area 20 includes asupply conveyor line 22 for supplying computer components 24 to aplurality of workstations, each indicated generally by the referencenumeral 26. Each of the workstations 26 is oriented perpendicular to thesupply conveyor line 22. The computer components 24 are tested at theworkstations 26, and, thereafter, are transferred to a delivery conveyorline 28, which is generally parallel to the supply conveyor line 22. Thedelivery conveyor line 28 delivers the computer components 24 forpackaging or additional testing.

Although the preferred embodiment of the invention is described inconnection with testing computer components 24, it will be readilyunderstood by those skilled in the art that the present invention can beapplied to workpieces other than computer components and for purposesother than testing, such as, for example, assembling products.

The conveyor lines 22, 28 and the juxtaposed workstations 26 definemultiple work areas 30 in which a number of workers may work. In orderto provide relatively free access into and out of the work areas 30, anaccess space 32 is provided between the workstations 26 and at least oneof the conveyor lines 22, 28 in a manner that will be described in moredetail below.

As shown in FIG. 4, each conveyor line 22, 28 includes a supportassembly 34. The support assembly 34 includes multiple pairs of verticalsupports 36. Each pair of vertical supports 36 may also includetransverse supports 38.

A conveyor system 42 is supported by the support assembly 34. Theconveyor 42 includes a pair of parallel rails 44 with a plurality oftransverse rollers 46 pivotally mounted for rotation therebetween.Preferably, the rollers 46 are driven by a motor and belt assembly (notshown). A stop plate 47 is provided at the ends of the conveyor system42 for preventing computer components from falling off the conveyorlines 22, 28.

FIGS. 4-12 illustrate the workstation 26 in greater detail. Theworkstation 26 is preferably located adjacent to the delivery conveyorline 28. However, it will be readily understood by those skilled in theart that the workstation 26 can be provided in a variety of locationsbetween the conveyor lines 22, 28 including, without limitation,adjacent to the supply conveyor line 22 or centered between the conveyorlines 22, 28. The workstation 26 includes a support assembly 48. Thesupport assembly 48 comprises multiple laterally extending bases 49. Aleg 50 extends vertically from each of the bases 49 and supports asupport frame 51.

A shelf assembly 52 extends vertically from the frame 51. The shelfassembly 52 includes multiple vertical main support members 54. The mainsupport members 54 are connected by upper and lower longitudinallyextending members 56, 57. The lower longitudinally extending member 57includes a plurality of power outlets (not shown). Upper and lower setsof braces 58, 60 are connected to the main support members 54 forsupporting an upper and a lower shelf 62, 64, respectively. The shelves62, 64 supports a variety of testing equipment (not shown) used fortesting the computer components 24. The testing equipment and computercomponents 24 are powered by the power outlets in the lowerlongitudinally extending member 57.

As illustrated in FIGS. 4-9, a conveyor support frame 66 is alsosupported by the support assembly 48. The conveyor support frame 66includes a pair of longitudinally extending beams 68. Each of thelongitudinally extending beams 68 includes an upper surface 69 (FIG. 9).The frame 66 includes a pair of laterally extending beams 70 that extendbetween the longitudinally extending beams 68 near opposite ends of thebeams 68. As illustrated in FIG. 9, the laterally extending beams 70include upper and lower surfaces 72, 74, respectively. A thirdlongitudinally extending beam 76 is supported by the upper surfaces 72of the laterally extending beams 70 (see FIGS. 8 and 9). Thelongitudinally extending beam 76 includes upper and lower surfaces 78,80. A first stop hole 82 (FIG. 9, 13) and a second stop hole 83 (FIG. 8)are provided in the upper surface 78 of the longitudinally extendingbeam 76.

A pair of longitudinally extending slide rails 88 are connected to theupper surface 69 of the longitudinally extending beams 68. Each sliderail 88 has a longitudinally extending base portion 90 and alongitudinally extending rod-shaped top portion 92.

A conveyor, indicated generally by the reference numeral 100, isslidably supported by the slide rails 88. The conveyor 100 includes apair of parallel side rails 102. A plurality of laterally extendingcross plates 103 are connected to the undersurface of the side rails102. A plurality of laterally extending rollers 104 extend between, andare rotatably mounted to, the side rails 102.

As illustrated in FIG. 5a, an end roller 106 is provided at the end ofthe rollers 104 closest to the delivery conveyor line 28. The end roller106 includes a laterally extending contact plate 108 that is welded to atop part of the roller 106. The end roller 106 also includes aconnecting lug 110 that is welded to a bottom part of the roller 106 atone end of the roller 106. A cylindrical stop member 111 protrudes froman inner side of the side rail 102. A retention spring 112 is providedbetween the connecting lug 110 and a connecting point 114 on the rail102.

A contact mechanism 118 is mounted to one of the aforementioned mainsupport members 54 adjacent to the delivery conveyor line 28. Thecontact mechanism 118 includes a bracket 120 mounted to the main supportmember 54 by a pair of threaded fasteners 122. A contact flange 124extends horizontally from the bracket 120 over one corner of theconveyor support frame 66.

As illustrated in FIG. 7a, a second end roller 126 is provided at theend of the rollers 104 near an end of the conveyor 100 closest to thesupply conveyor line 22. A laterally extending contact plate 128 iswelded to a top part of the roller 126. A connecting lug 130 is weldedto a bottom part of the roller 126 near one end of the roller 126. Acylindrical stop member 131 protrudes from an inner side of the siderail 102. A retention spring 132 is provided between the connecting lug130 and a connecting point 116 on the side rail 102.

As illustrated in FIGS. 5a and 9, slidable receivers 134 are attached tothe undersurface of the cross plates 103. The receivers 134 are known inthe art as pillow block linear bearings. The receivers 134 slidablyreceive the slide rails 88 so as to allow shifting and sliding movementof the conveyor 100. The receivers 134 engage the slide rails 88 so thatthe conveyor 100 is prevented from disengaging the rails 88. Eachreceiver 134 includes a mounting portion 136 mounted to the undersurfaceof each of the cross plates 103 and a receiving portion 138 thatslidably receives the rod-shaped top portion of each of the slide rails88.

As illustrated in FIGS. 8-12, a locking assembly, indicated generally bythe reference numeral 140, is provided on an upper surface of one of thecross plates 103. The locking assembly 140 has a T-shaped handle 144with a threaded end 146. A bolt 148 cooperates with the threaded end 146of the handle 144 for attaching the handle 144 to a first connectingportion 150 of a ramp member 152. The ramp member 152 is slidablysupported by a flat raised portion 151 of the cross plate 103. The rampmember 152 has a sloping upper surface 153. A horizontally extendingeyebolt 156 is mounted to a second connecting portion 158 of the rampmember 152. A retention spring 160 connects the eyebolt 156 to a secondvertically extending eyebolt 162, which is mounted to the cross plate103.

A U-shaped bracket 164 includes a pair of vertical legs 165 (FIG. 13)that straddle the raised portion 151 and ramp member 152. The verticallegs are connected by an upper bridge portion 168. The U-shaped bracket164 is mounted to an upper surface of the cross plate 103. The upperbridge portion 168 includes a receiving hole 170. The raised portion 151and the cross plate 103 also include aligned receiving holes 174 that,along with receiving hole 170, receive a locking pin 176. A first wheelassembly 178 includes a pair of wheels 179 rotatably mounted to the pin176 along opposite sides of the pin 176. The wheels 179 are preferablyhalf inch bearings. A second wheel assembly 180 includes a wheel 181rotatably mounted within the bottom of the pin 176 for rotation in adirection that is perpendicular to the rotational direction of the otherwheels 178. The wheel 181 is preferably a three-eighths inch bearing. Aplate 182 is supported by the first wheel assembly 178. The plate 182also includes a receiving hole for receiving the lock pin 176. Acompression spring 184, which also receives the pin 176, is providedbetween the upper surface of the plate 182 and the undersurface of theupper bridge portion 168.

The operation of the locking assembly 140 of the present invention willnow be described. FIG. 11 illustrates the locking assembly 140 in alocked position. In the locked position, the locking pin 176 engages oneof the aforementioned pin holes 82, 83 of the longitudinally extendingbeam 76 and the ramp member 152 is provided in a home position. Tounlock the locking assembly 140, the locking pin 176 must be removed ordisengaged from whichever hole 82, 83 of the beam 76 the pin 176 isdisposed within. This is accomplished by pulling on the T-shaped handle144 in a laterally outward direction so that the ramp member 152 moveslaterally outward. Movement of the ramp member 152 in this manner causesthe wheels 178 to roll up the slope surface 153 of the ramp member 152.This causes the locking pin 176 to move upwardly and disengage the pinhole 82, 83.

To lock the locking assembly 140, the locking pin 176 must first bedisposed over one of the pin holes 82, 83 so that it may engage the pinhole 82, 83. To accomplish this, the T-shaped handle is released so thatthe retention spring 160 can restore the ramp member 152 to its homeposition. Once the ramp member 152 is in its home position, therestoring force in the compression spring 184 forces the pin 176downwardly into the hole 82, 83, or, in the event the pin 176 is notdisposed over one of the pin holes 82, 83, against the upper surface 78of the longitudinally extending beam 76. If the pin 176 is not disposedover one of the pin holes 82, 83, the compression spring 184 causes thelower wheel 181 on the bottom of the pin 176 to be forced against theupper surface 78 of the beam 76. As the conveyor 100 is shifted, thelower wheel 181 rolls along the upper surface 78 of the beam 76. Whenthe conveyor 100 is shifted to a position where the locking pin 176 isdisposed over one of the holes 82, 83 of the beam 76, the compressionspring 184 forces the pin 176 into the hole 82, 83 so as to lock thelocking assembly 140.

The operation of the workstation 26 of the present invention will now bedescribed in connection with FIGS. 4-7. In FIG. 4, the conveyor 100 ofthe workstation 26 is illustrated in a home position. The conveyor 100is predominantly provided in the home position because this position isideal for testing the components 24 with the aforementioned testingequipment.

In order to load the conveyor 100 with a plurality of computercomponents 24 for testing, the conveyor 100 is shifted to a loadingposition (FIG. 6). This is accomplished by first pulling outwardly onthe T-shaped handle 144 so as to disengage the locking pin 176 from thefirst stop hole 82 of the longitudinally extending beam 76 as describedabove. The conveyor 100 is then shifted to the loading position. In theloading position, the locking pin 176 is disposed over the second stophole 83 (FIG. 8). Before or when the conveyor 100 is shifted to theloading position, the operator allows the handle 144 to be restored toits laterally inward position so that the locking pin 176 can engage thesecond pin hole 83 of the beam 76. This causes the conveyor 100 to belocked in the loading position so that the conveyor will not slide whencomputer components are loaded onto the conveyor 100.

As illustrated in FIGS. 7a-c, as each computer component 24 isindividually loaded onto the conveyor 100, the computer component 24contacts the contact plate 128 of the end roller 126. This causes theend roller 126 to rotate from its original position (FIG. 7a) to a fullyrotated position (FIG. 7c). As the end roller 126 rotates to a fullyrotated position, the retention spring 132 stretches. In return, thespring 132 pulls on the connecting lug 130. When the computer component24 is moved beyond the contact plate 128 of the end roller 126, thespring 132 restores the end roller 126 to its original position (FIG.7a). The end roller 126 is prevented from rotating in the oppositedirection by the stop member 131. As a result, the contact plate 128prevents computer components 24 from falling off the conveyor 100 andbecoming damaged. After all of the computer components 24 are loadedonto the conveyor 100, the locking assembly 140 is disengaged and theconveyor is shifted back towards the home position (FIG. 4) so that thecomponents 24 may be tested.

As illustrated in FIGS. 5a-c, as the conveyor 100 approaches the homeposition, the contact flange 124 of the contact mechanism 118 abuts thecontact plate 108 of the end roller 106. This causes the end roller 106to rotate from its original position (FIG. 5a) to a fully rotatedposition (FIG. 5c). When the end roller 106 is in the fully rotatedposition, the contact plate 108 does not inhibit transferring thecomputer components 24 from the conveyor 100 to the delivery conveyorline 28. When the end roller 106 is rotated, the retention spring 114 isstretched. Thus, when the conveyor 100 is shifted to a position wherethe contact flange 124 does not abut the contact plate 103, the spring114 restores the end roller 106 to its original position. The end roller106 is prevented from rotating in the opposite direction by the stopmember 111. As a result, the computer components 24 are prevented fromfalling off the conveyor 100 and becoming damaged when the conveyor 100is not in the home position.

Once the conveyor 100 is completely shifted to the home position, theoperator engages the locking pin 176 with the first stop hole 82 of thelongitudinally extending beam 76 to lock the conveyor 100 in the homeposition. This prevents the conveyor 100 from accidentally shifting. Thecomputer components 24 are tested and transferred to the deliveryconveyor line 28 to be delivered for packaging or further testing.

The shifting conveyor 100 of the workstation 26 of the present inventionprovides continued access space 32 between each workstation 26 and atleast one of the conveyor lines 22, 28 except when conveyor 100 isperiodically shifted to a loading position for a short period of time inorder to load the components 24 onto the conveyor 100 for testing.Although the access space 32 is preferably located between the supplyconveyor line 22 and the workstation 26, it will be readily understoodby those skilled in the art that the access space 32 may be provided ina variety of locations without departing from the spirit or scope of theinvention such as, but not limited to, between the delivery conveyorline 28 and the workstation 28 and between the workstation 26 and bothconveyor lines 22, 28. This generally continued access space 32 was notprovided in gravity gate equipped workstations in the past. The accessspace 32 allows the workers to freely pass into and out of the workareas 30. Not only is this convenient for the workers, but it saves theworkers time and helps prevent the workers from being trapped within oneof the work areas 30 during an emergency. The shifting conveyor 100 alsoeliminates the previously discussed problems with gravity gates such asthe potential injury they can cause to workers and the potential damagethey can cause to components.

It should be readily apparent from the foregoing description of thepreferred embodiment of the invention that the shifting conveyor of theworkstation of the present invention eliminates the problems withgravity gate workstations. Of course, the foregoing description is thatof a preferred embodiment of the invention, and various changes andmodifications may be made without departing from the spirit and scope ofthe invention as defined by the appended claims.

What is claimed is:
 1. A workstation for working on a workpiece betweena first conveyor line and a second conveyor line, the workstationcomprising:a support assembly including at least one longitudinallyextending rail, said rail having a length between a first end and asecond end which is less than a distance between said first conveyorline and said second conveyor line such that a space is provided betweensaid first end of said rail and said first conveyor line whereby aworker can walk therethrough; a longitudinally extending conveyor, saidconveyor having respective first and second ends, said conveyor slidablymounted to said longitudinally extending rail for slidable longitudinalmovement between at least a home position wherein said second end ofsaid conveyor is proximate said second end of said rail where saidconveyor is provided for working on said workpiece and a second positionwhere said first end of said conveyor is positioned adjacent to saidfirst conveyor line, said conveyor having a longitudinal length sizedand configured to form an access space which provides an unobstructedpathway from a first side of said conveyor to a second side of saidconveyor between said first end of said conveyor and said first conveyorline when said conveyor is positioned in said home position.
 2. Theworkstation of claim 1, wherein said conveyor is slidably mounted tosaid rail by at least one slidable receiver positioned along anundersurface of said conveyor, said receiver slidably mounted to saidrail for shifting movement of said conveyor in a longitudinal direction.3. The workstation of claim 1, wherein a pair of stop devices areprovided near opposite ends of said conveyor which prevent the workpiecefrom accidentally falling off said conveyor.
 4. A workstation forworking on a workpiece between a first conveyor line and a secondconveyor line, the workstation comprising:a support assembly includingat least one longitudinally extending rail, said rail having a lengthbetween a first end and a second end which is less than a distancebetween said first conveyor line and said second conveyor line such thata space is provided between said first end of said rail and said firstconveyor line; a longitudinally extending conveyor, said conveyor havingopposite ends, said conveyor slidably mounted to said longitudinallyextending rail for slidable movement between at least a home positionwhere said conveyor is predominantly provided for working on saidworkpiece and a second position where one end of said conveyor isprovided adjacent to a conveyor line, said conveyor having alongitudinal length that allows an access space between said conveyorand said conveyor line when said conveyor is provided in said homeposition, wherein said conveyor is slidably mounted to said rail by atleast one slidable receiver provided along an undersurface of saidconveyor, said receiver slidably mounted to said rail for slidingmovement of said conveyor in a longitudinal direction, and wherein apair of stop devices are provided near opposite ends of said conveyorwhich prevent the workpiece from accidentally falling off said conveyor,wherein each of said stop devices includes a roller with a laterally andvertically extending plate.
 5. The workstation of claim 4, wherein saidroller of at least one of said stop devices rotates in a firstrotational direction from a first orientation in which said laterallyand vertically extending plate is vertical to a second orientation inwhich a workpiece can pass over said plate in a first longitudinaldirection, said roller rotating in an opposite rotational direction toreturn said laterally and vertically extending plate to said firstorientation to block movement of said workpiece in a second longitudinaldirection opposite said first longitudinal direction.
 6. The workstationof claim 5, further including a spring which biases said stop plate toan upright position so as to prevent the workpiece from falling off theconveyor.
 7. The workstation of claim 1, wherein means for preventing aworkpiece from falling off said conveyor are provided near at least oneend of said conveyor.
 8. The workstation of claim 7, wherein saidpreventing means are made ineffective when said conveyor is provided inat least said second position.
 9. The workstation of claim 1, whereinsaid conveyor includes a locking mechanism, said locking mechanismcooperating with said supporting assembly for locking said conveyor insaid home and second positions.
 10. A worktable positionable betweenfirst and second conveyor lines, wherein products are conveyed betweensaid worktable and said first conveyor line and products are conveyedbetween said worktable and said second conveyor line, said worktablecomprising:a top surface, said top surface comprising a conveyor whichpermits products to be moved across said top surface; and a moveablesupport for said top surface, said moveable support permitting lateralmovement of said top surface from a first position where said topsurface is proximate to said first conveyor line to a second positionwhere said top surface is proximate to said second conveyor line, saidmoveable support forming an access space between said top surface andsaid final conveyor line when said top surface is in said secondposition, said access space providing an unobstructed pathwayperpendicular to said conveyor to permit a worker to move from a firstlongitudinal side of said conveyor across to a second longitudinal sideof said conveyor.
 11. The worktable as defined in claim 10, whereinsufficient space is provided between said worktable and said firstconveyor line when said top surface is in said second position to permita person to walk unimpeded between said worktable and said firstconveyor line.
 12. A conveyance system comprising:a support assembly; alongitudinally extending conveyor, said conveyor having first and secondends and a longitudinal length between said first and second ends, saidconveyor slidably mounted to said support assembly for slidablelongitudinal movement between a first position and a second position,said first end of said conveyor being cantilevered from said supportassembly and positioned proximate to a first conveyor line in said firstposition and said second end being spaced apart from a second conveyorline in said first position, said first end of said conveyor beingspaced apart from said first conveyor line in said second position toform an access space between said first end and said first conveyorline, said access space providing an unobstructed pathway perpendicularto said conveyor to permit a worker to move from a first longitudinalside of said conveyor to an opposite longitudinal side of said conveyoracross.
 13. The workstation of claim 12, wherein said access space issized and configured to permit a person to walk unimpeded through saidaccess space.